Is anecdotal evidence dangerous?

[nereas]

LOL. What an obvious and stupid strawman you attempt to construct. ...



Back to your post.

Did I make any point whatever about what I think about the US Navy tables? No.
Did I say anything about diving to 100m? No.
Did I say I thought they were safe? No.
Did I say I thought they were unsafe? No.

So don't try and put words in my mouth because you'll just end up looking more stupid.

My point was that either your starting point for your posted argument is wrong, or Thal is lying.

It is hard to tell when Thal is being ironic. He is such an extremely bright person that his methods of debate are normally way above everyone else's comprehension. However I believe that he does not lie.

And I thought it was a great strawman because it completely overturned your argument by logical extension, as evidenced by your speedy redaction.

 

[Geoff_H]

On a related but side issue, I wonder if there has been any attempt to quantify how much of an increased risk of bubble formation there is with increasing age and decreasing fitness?

I know we are taught that both age and fitness will increase the risk of DCS, but I wonder how much of an increase there is? 1% more chance? 10% more chance? 1000% ?

 

[Colliam7]

I have read so many posts that use only anecdotal evidence to support a particular point of view. To me this is down right dangerous in some cases. How many times have we all read “ I’ve been to 160’ fsw on air and did fine” or “I came up from 100’ and did not do a safety stop” or “I don’t get narcked at 120’ fsw”. This sends a message that if I did it, you should be fine so go ahead and try it!

A very good point, although I might take a slightly different view of the message implied by such statements, at least in some cases. If someone asks, 'Can it be done?' (whatever 'it' might be), and a respondent says, 'Yes, and I have done it.', that is not necessarily a recommendation for others to do the same. It is a factual answer to a question. There is 'flip side' to the issue, as well. Not infrequently, points of view are (firmly) expressed on the basis of theoretical concerns, which have not been verified by science, either. Using the example of depth and narcosis, as I am one who has said, 'I have dived to 165 ft on air and did fine.' - there are those who have said they will not dive below 100ft except on mix. A reasonable personal choice, which is appropriately offered for others on SB to consider. What are the objective data to support that anecdotal view? What are the objective data to suggest that outcomes (safety, enjoyment, etc,) are statistically influenced by the use of air or mix for diving in the 100 - 160ft range? And, I am certainly not arguing against the use of mix at a particular depth by any means, only illustrating the challenges we face when there are simply no objective data. And, at the risk of really opening Pandora's box, I would offer the opinion that much of the debate over agencies, standards, etc., while stimulating and thought-provoking, falls in the same category. It is simply not possible to make objective, statistically sound, determinations regarding comparative safety records, or even trends.

I believe in the premise that science trumps anecdotal evidence every time. So when someone presents a situation where the only evidence is anecdotal, do more research before trusting the information.

Sound advice. Part of the value of SB is that it allows individuals to offer opinions, AND to supply the basis of those opinions, which includes the logic and reasoning but also supporting, first person experience in many cases. The opinions should be, and for the most part are, offered with no warranties implying that they can be applied to other individuals (or even to the same individual at any other point in the future for that matter). The fundamental problem we have is that there are very little, in fact almost no, data to guide many of the decisions we make as divers make. Science does trump anecdotal evidence. We need more applied science.

 

[WJL]

I believe in the premise that science trumps anecdotal evidence every time. This not to say some have in fact done some of these things but is it safe for anyone, no. So when someone presents a situation where the only evidence is anecdotal, do more research before trusting the information.

You are bumping into the paradox of how people assess "evidence." I have to deal with this, and think hard about this, pretty regularly in my real job as a trial attorney. My experience is that most people are more persuaded by stories with human interest than by surveys or statistics. Their heads may tell them that the statistics are right, but what grabs their heart is the story of what actually happened to someone.

This phenomenon is part of the reason that people find it almost impossible to assess an accident or tragedy without engaging in the luxury of hindsight. An unlikely event does not seem so preposterous after it has already occurred. So, for example, people look at all the indicators that existed before 9-11 about terrorists and airplanes, and are outraged that the threat of deliberate airplane attack was deemed minimal before the WTC actually fell down. After seeing the smoking rubble, it is almost impossible to really and truly put yourself in the position of a security analyst on 9-10 to assess the significance of reports of Muslims taking flying lessons.

People are constructed to respond to the emotion of stories, i.e., anecdotes. Never discount the power of emotion to shape people's thinking. Bemoaning people's visceral response to anecdotes is a losing proposition.

 

[Teamcasa]

Bill, I think we are on the same page in a weird way. I have worked with many attorneys and employ two. I have a great respect for their unique way of looking at things, analyzing risks and digging until they find the truth. Using analogies, anecdotes to relate a unique or complicated situation into something everyone can understand are their tools of the trade.

When it comes to diving, my point is a simple one. I generally don’t trust anecdotal evidence unless it has some factor that gives it a base in fact. I doubt you do either.

 

[Thalassamania]

I work with (and for) lawyers all the time. They drive me nuts, I need 90% confidence in something before I believe it, to the lawyers, well ... if it ever happened once, that's reality.

 

[WJL]

When it comes to diving, my point is a simple one. I generally don’t trust anecdotal evidence unless it has some factor that gives it a base in fact. I doubt you do either.

I agree with your point personally. And you're right in your suspicions. I personally find studies and statistics and controlled experiments much more persuasive than the story of what happened to Aunt May that time she ate a banana right after drinking a Coke. But I have had to learn the hard way that most people find the Aunt May story more compelling and persuasive than any number of scientific studies. So anecdotes may be lacking in scientific validity, but they have great emotional weight.

I guess the point I'm getting to is that trying to tell people not to give undue weight to anecdotal evidence is a Quixotic endeavor - your goal is admirable, but your chance of success is low.

 

[Teamcasa]

I agree with your point personally. And you're right in your suspicions. I personally find studies and statistics and controlled experiments much more persuasive than the story of what happened to Aunt May that time she ate a banana right after drinking a Coke. But I have had to learn the hard way that most people find the Aunt May story more compelling and persuasive then any number of scientific studies. So anecdotes may be lacking in scientific validity, but they have great emotional weight.

I guess the point I'm getting to is that trying to tell people not to give undue weight to anecdotal evidence is a Quixotic endeavor - your goal is admirable, but your chance of success is low.

I knew the job was dangerous when I took it!

 

[WJL]

I knew the job was dangerous when I took it!

Here's hoping that there's a Dulcinea to reward your bravery.

 

[fweber]

I know this thread was started with the best of intentions. And, for the most part, it has been a reasonably civil exchange. It's interesting to consider that when it comes to best or most current practice, they are largely supported anecdotally or even theoretically, but not yet by scientific study.

I'm sure most of you may have already read the thread I'll link below. But, if not, it provides a wonderful example of the issues involved with this subject of anecdotal evidence vs. theoretical science vs. scientific study. It also does a decent job of defining the difference between probabilistic deco models vs. theoretical models.

The Deco Stop

thoughts?